Preparation of aluminium for electroplating.



UNITED PATENT OFFICE;

FRANK s. LoEB, or NEW, KENsINGToN, rENNsYLvA IA.'

PREPARATION OIFYALUMINIUM FOR ELlEci'I oP'LA'nNc.

SPECIFICATION ramiig sa'orneaers Patent No; 030,246, datedAugusir 11899. pp at qd September 8,1898. Serial lie-690.210. (a al a To all whomit may concern:

. Be it known that I,FRANK S. LOEB, of New Kensington, in the county ofAllegheny and State of Pennsylvania, have iiivented a new and usefulImprovement in the Preparation of Aluminium forElectroplating, of whichthe following is a specification.

The object of my invention is to electroplate aluminium with othermetals, an object which, although often" tried, has not hitherto beenaccomplished satisfactorily.

To prepare the aluminium to receive the electrodeposit, I treat it withone of the acids of the halogen group, preferably hydrofluoric acid,which I have discovered to be much the best and to which I intend tovmake specific claims in addition to the broader claims. Then I quickthe aluminium with a mercury solution, preferablyrassolution composed.of nitrate of mercury, to whichis added-a cyanid. Then after thequicking I treat thealuminium again in the acid-bath, after which it isready to receive the electrodeposit. By thus treating the aluminium withacid after it has been quicked the plating of metal subsequentlydeposited thereon is rendered very adherent and durable, much more sothan would'be the case if the guicked aluminium were put in theplating-bath without such retreatment with acid.

-I shall now describe the preferable compositions and preferableproportions which I have used in this preparatory'treatment and inelectroplating, promising that within the scope of my claims the samemay be variedby the skilled electrometallurgist in many way.

The hydrofluoric acid is preferably dilute, made by adding, say,twenty-fi ve cubic centimeters strong acid to two thousand cubiccentimeters water. The aluminium, having first been cleansed to removegrease, dirt, 8m.

and preferably rinsed in .hot water, is immersed in the hydrofluoricacid until were gen gas is freely evolved from it.

Thequicking solution into which the aluminiumis put after treatment intheh'ydrofiuoric acid is preferably composed of fifty '6. grams mercurydissolved in, say, onefhun-j; d-redcubic centimeters strong nitric acid,this being added to two thousand cubic centimefters water and thirtygrams potassium cya'nid. The time of immersion of the alumini um in thequicking bath shoulddepend upon the strength of the bath. With a bathcomsuflice. Otherquickingsolutionsof mercury may be used. 1

The hydrofluoric-acid aluminium is introduced after its removal from thequicking-bath may be constitutedin the same manner as the acid-bathabove gas.

' aluminium is put after its second acid treatment is an alkaline orneutral solution, which when copper is to. be deposited is preferablyconstituted as follows, and used hot-say at a thick paste with water andadd eight ounces sodium carbonate dissolved in two quarts of water. In aseparate vessel I dissolve eight ounces sodium bisulfite in two quartswater and add this sodium-bisulfite solution to the I also dissolve sixounces potassium cyanid in three quarts water and add it to the previousmixture, and then add five quarts water, making it up to three gallons,when the bath is ready for use. When used, I connect a copper thenegative wire objects to be plated. When in'a suitable manner-sayby'rinsing in run sawdust. polished, or bufied without injuring the de-For electrodepositingbrassbn aluminium an "alkaline brass, both ofcomposition analogous v2 ,to thos'e'above described,m ay be used. A goodb'rassfplating bath is made of five ounces cop-r grac'etate and'fiv-eounces zinc chlorid fused,

ved inwater. To this are added ten dinm bisulfite, th'e'ni'sev'en ouncespotassium cyauid and waterenough to make up, say,

three gallons. 'i p a pounded as just stated about five seconds willanode to the positive wire and suspend from 5 sufliciently plated, thearticle may be cleaned bath into which the described,and the length ofimmersion should be sufiieient to' cause evolution of hydrogen j Theelectroplating solution into which the temperaturaoffnomliifl,v1191.180. Fa renhe I make eight ounces of copper acetate to a is ivcopper-acetate and sodium-carbonate solution.

ning water, then in hot water, and dried in It can then bescratch-brushed, y 0 posited film, which is strong and adherent, so

and forth repeatedly without cracking the 1 n s'sodiumcarbonate and fiveounces so- I g; r V 630,246

'1 i "Io plate'with silver, the following is'a good bath: three ouncessilver chlorid, eight ounces potassium cyanid, and eight ounces sodium Iv carbonate dissolved in, say, one gallon water.

The foregoing plating-baths are i-llus'trm tive, and as the essence ofmy invention is' not the depositing of any particular metal or 'ofdepositing a metal from any particular alkaline; solution I deem itunnecessary further "toelaborate onthis point. v E Icla'im-.

; 1.- The methodrot preparing aluminium for electroplating, whichconsists intreatin'g the aluminium with hydrofluoric acid-,thenquickaluminium and then treating the quicked aluminium with hydrofluoricacid; substantially as described. 1

1 In testimony whereof I'havehereunto set my hand.

r "FRANK S. LOEB,

Witnesses:- I I j GEORGE B. BL MMI G, s

' G.I.'H0 1)sH1P. f

